An example of this type of image sensor module is disclosed in JP-A 2002-247288. The image sensor module disclosed in this publication comprises an image sensor chip mounted on a substrate, and a case enclosing the image sensor chip on the upper surface of the substrate. The case holds an image-forming lens firmly in place. The image of the subject is formed on the image sensor by the function of the image-forming lens. The image sensor chip outputs an image signal with an output level corresponding to the image of the subject.
However, the conventional technology has only a single optical unit employing an image-forming lens, while the focal distance of the image-forming lens is fixed. The view angle when imaging the subject (the area of the subject which may be obtained as an image through the lens) is fixed and diversity in imaging is limited.
A zoom lens unit (a lens unit having a function to vary the focal length) may be employed as means for changing the view angle. However, a zoom lens unit has a precision mechanism to move a simple lens accurately, and cost is therefore very high. Further, since a zoom lens unit comprises a plurality of simple lenses arranged at appropriate spacing on an optical axis, it becomes large. A zoom lens unit is not appropriate as a component for an image sensor module which requires cost and size reduction.